The present invention relates to a blow-by gas processing apparatus which is applicable to an internal combustion engine provided with a supercharger.
A vehicle internal combustion engine can be provided with, for example, a blow-by gas processing apparatus. The blow-by gas processing apparatus recirculates a combustion gas leaking to a crank chamber from a gap between a cylinder and a piston of the engine, that is, a blow-by gas to an intake passage. Specifically, an intake negative pressure generated in a portion of the intake passage in a downstream side of a throttle valve draws the blow-by gas in an interior of the engine so as to circulate in a breather passage. The blow-by gas is returned to the intake passage from the breather passage, is again fed to the combustion chamber, and is burned. Accordingly, it is possible to reduce a discharge amount of a hydrocarbon (HC) to the atmosphere. Further, it is possible to inhibit the blow-by gas from deteriorating oil in the engine. As mentioned above, the blow-by gas processing apparatus ventilates the interior of the engine.
In the case that the supercharger is provided in the internal combustion engine, if the supercharger is operated, the intake negative pressure is lost.
Japanese Laid-Open Utility Model Publication No. 5-87213, Japanese Laid-Open Patent Publication No. 2006-144686 and Japanese Laid-Open Patent Publication No. 2004-60475 each disclose a blow-by gas processing apparatus which is applicable to an internal combustion engine provided with a supercharger.
As shown in FIG. 12, the blow-by gas processing apparatus disclosed in Japanese Laid-Open Utility Model Publication No. 5-87213 is provided with an introduction passage 101, a first breather passage 102, and a second breather passage 103. An intake passage 105 is provided with an upstream portion 105a which is provided on an upstream side of a compressor 106a of a supercharger 106, an intermediate portion 105b which is provided between the compressor 106a and a throttle valve 109, and a downstream portion 105c which is provided on a downstream side of the throttle valve 109. The introduction passage 101 connects the upstream portion 105a with an interior of a head cover 104 of the engine 100. The introduction passage 101 is provided with a check valve 107. The first breather passage 102 connects an interior of a crankcase 108 with the downstream portion 105c. The first breather passage 102 is provided with a positive crankcase ventilation valve (a PCV valve) 110. The second breather passage 103 connects the interior of the crankcase 108 with the upstream portion 105a. The second breather passage 103 is provided with a check valve 111.
In the case that the supercharger 106 is not operated, that is, at a non-supercharging time, an intake negative pressure is generated in the downstream portion 105c. Accordingly, as shown by filled-in arrows in FIG. 12, the blow-by gas in the engine 100 flows through the first breather passage 102 and is drawn (recirculated) into the intake passage 105. In the same manner, as shown by the filled-in arrows, an intake air flows through the introduction passage 101 so as to flow into the interior of the engine 100, and makes the interior of the engine 100 close to the atmospheric pressure.
Further, in the case that the supercharger 106 is operated, that is, at a supercharging time, the negative pressure is generated in the upstream portion 105a. As a result, as shown by open arrows in FIG. 12, the blow-by gas in the engine 100 can flow through the second breather passage 103 so as to be drawn into the intake passage 105.
However, in the blow-by gas processing apparatuses in the publications mentioned above, it is practically impossible to introduce the intake air into the interior of the engine at the supercharging time.
As shown in FIG. 13, the blow-by gas processing apparatus disclosed in Japanese Laid-Open Patent Publication No. 2006-144686 is provided with an introduction passage 121, a breather passage 122, and a common passage 123. An intake passage 124 is provided with an upstream portion 124a which is provided on an upstream side of a compressor 125a of a supercharger 125, an intermediate portion 124b which is provided between the compressor 125a and a throttle valve 126, and a downstream portion 124c which is provided on a downstream side of the throttle valve 126. The introduction passage 121 connects the intermediate portion 124b with a chain case 127 of the engine 120. The introduction passage 121 is provided with a check valve 128. The breather passage 122 connects an interior of a crankcase 129 with the downstream portion 124c. The breather passage 122 is provided with a PCV valve 130. The common passage 123 connects an interior of a head cover 131 with the upstream portion 124a. 
At the non-supercharging time, an intake air existing within the upstream portion 124a flows through the common passage 123 so as to flow into the engine 120, and makes the interior of the engine 120 close to the atmospheric pressure. An intake negative pressure is generated in the downstream portion 124c. As a result, the blow-by gas in the engine 120 flows through the breather passage 122 so as to be drawn into the intake passage 124.
At the supercharging time, the intake air within the intermediate portion 124b flows through the introduction passage 121 so as to flow into the interior of the engine 120, thereby making the interior of the engine 120 higher pressure than the upstream portion 124a. Accordingly, the blow-by gas in the engine 120 flows through the common passage 123 so as to be drawn into the intake passage 124.
As a result, at both of the supercharging time and the non-supercharging time, the blow-by gas in the engine 120 is recirculated to the intake passage, and the intake air can be introduced to the interior of the engine 120. However, the blow-by gas flow in the engine 120 is different between the supercharging time and the non-supercharging time. Further, the intake air flow in the engine 120 is different between the supercharging time and the non-supercharging time. In other words, filled-in arrows and open arrows shown in FIG. 13 are directed to opposite directions to each other. As a result, the blow-by gas flow and the intake air flow are possibly disturbed in the engine 120 each time there is a switch between the supercharging time and the non-supercharging time. In other words, these flows can stagnate temporarily. Further, the blow-by gas discharged from the interior of the engine 120 can be again returned to the interior of the engine 120. Further, the intake air introduced to the interior of the engine 120 can be again returned to the outer portion. This can prevent an efficient ventilation of the interior of the engine 120. Particularly, in the case that the engine 120 is an in-vehicle internal combustion engine, the supercharging time and the non-supercharging time can be frequently switched in such a manner as to correspond to a change of the operating state of the engine 120. Accordingly, an efficient ventilation of the interior of the engine 120 is desired.
As shown in FIG. 14, the blow-by gas processing apparatus disclosed in Japanese Laid-Open Patent Publication No. 2004-60475 is provided with a first common passage 141 and a second common passage 142. An intake passage 143 is provided with an upstream portion 143a which is provided on an upstream side of a compressor 147a of a supercharger 147, an intermediate portion 143b which is provided between the compressor 147a and the throttle valve 144, and a downstream portion 143c which is provided on a downstream side of the throttle valve 144. The first common passage 141 connects an interior of an engine 140 with the downstream portion 143c. The first common passage 141 is provided with a PCV valve 145, and a bypass passage 146 bypassing the PCV valve 145. The second common passage 142 connects the interior of the engine 140 with the upstream portion 143a. 
At the non-supercharging time, the intake negative pressure is generated in the downstream portion 143c. As a result, the blow-by gas in the engine 140 flows through the first common passage 141, and is drawn into the downstream portion 143c. The intake air within the upstream portion 143a flows through the second common passage 142 so as to flow into the interior of the engine 140.
At the supercharging time, the intake air within the downstream portion 143c flows through the first common passage 141 and the bypass passage 146, and flows into the interior of the engine 140. Since the negative pressure is generated by the supercharger 147 in the upstream portion 143a, the blow-by gas in the engine 140 flows through the second common passage 142 so as to be drawn into the intake passage 143.
In this case, as shown in FIG. 14, filled-in arrows and open arrows are directed to opposite directions to each other. In other words, the blow-by gas flow in the engine 140, and the intake air flow in the engine 140 are inverted between the supercharging time and the non-supercharging time. Accordingly, if the supercharging time and the non-supercharging time are switched frequently, the ventilation efficiency in the engine 140 is lowered.